Monocrystalline magneto resistance element, method for producing the same and method for using same

ABSTRACT

To provide a key monocrystalline magnetoresistance element necessary for accomplishing mass production and cost reduction for applying a monocrystalline giant magnetoresistance element using a Heusler alloy to practical devices. A monocrystalline magnetoresistance element of the present invention includes a silicon substrate 11, a base layer 12 having a B2 structure laminated on the silicon substrate 11, a first non-magnetic layer 13 laminated on the base layer 12 having a B2 structure, and a giant magnetoresistance effect layer 17 having at least one laminate layer including a lower ferromagnetic layer 14, an upper ferromagnetic layer 16, and a second non-magnetic layer 15 disposed between the lower ferromagnetic layer 14 and the upper ferromagnetic layer 16.

RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 15/424,515 filed Feb. 3, 2017, which claims the benefit of thefiling date pursuant to 35 U.S.C. § 119(e) of JP2015-237601 filed Dec.4, 2015, all of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a magnetoresistance element having aferromagnetic thin film preferably used as an electrode material of atunnel magnetoresistance element, a current-perpendicular-to-plane giantmagnetoresistance element, or the like, particularly to amonocrystalline magnetoresistance element obtained by epitaxiallygrowing a (001) plane of a ferromagnetic thin film on a Simonocrystalline substrate having a large diameter.

In addition, the present invention relates to a device using themonocrystalline magnetoresistance element.

BACKGROUND ART

A ferromagnetic thin film of Fe, FeCo, or the like is often used as anelectrode material of a tunnel magnetoresistive (TMR) element or acurrent perpendicular to plane-giant magnetoresistance element. Many ofthese ferromagnetic materials have body-centered cubic lattice (bcc)structures. These magnetoresistance elements are used for a reproductionhead of a hard disc drive (HDD) or a recording element of amagnetoresistance random access memory (MRAM). In addition, a currentperpendicular to plane-giant magnetoresistance (CPP-GMR) element havinga Co-based Heusler alloy having a high spin polarizability as aferromagnetic layer has a lower element resistance than a tunnelmagnetoresistance element, and therefore application thereof as amagnetic head for a next-generation high density HDD is expectedstrongly (refer to Patent Literatures 1 and 2).

However, all of these magnetoresistance elements in practical use havepolycrystalline structures. For example, a tunnel magnetoresistanceelement in which magnesium oxide (MgO) is a tunnel barrier using a CoFeBferromagnetic material as an electrode is formed by the followingmanufacturing process.

(i) Amorphous CoFeB is formed on amorphous Ta formed on a Cu electrode.

(ii) A MgO tunnel barrier growing in a strong (001) orientation isformed on the amorphous CoFeB in (i).

(iii) Amorphous CoFeB is further formed on the MgO tunnel barrier in(ii).

(iv) The above formed multilayer film is subjected to a heat treatment,and the amorphous CoFeB is crystallized into CoFe having a body-centeredcubic lattice structure.

(v) At this time, each crystal in the polycrystal has a consistencyrelation of (001)[001]CoFe//(001)[011]MgO using a Miller index, andtherefore a tunnel electron is spin-polarized highly.

A high tunnel magnetoresistance is exhibited by (i) to (v).

Each crystal in a polycrystal crystallized from amorphous FeCoB isrequired to have a consistency relation of (001)[001]CoFe//(001)[011]MgOwith an oxide barrier such as MgO or MgAlO in order to obtain a hightunnel magnetoresistance. Recently, a tunnel barrier of MgAl₂O₄,non-stoichiometric MgAlO, or the like is used in addition to MgO. In anycase, in order to exhibit a high tunnel magnetoresistance, aferromagnetic body having bcc as a basic structure, such as Fe, Co, analloy thereof, or a Co-based Heusler alloy is required to be oriented ina (001) direction of a Miller index.

Meanwhile, a current perpendicular to plane-giant magnetoresistance(CPP-GMR) element has a structure in which a laminated film offerromagnetic layer/non-magnetic layer/ferromagnetic layer is formedinto a pillar having a submicrometer-size or less. When a current flowsin a pillar, an electric resistance is changed according to a relativeangle of magnetization of two ferromagnetic layers, and therefore amagnetic field can be detected electrically. However, when a generalferromagnetic body such as CoFe is used, a magnetoresistance (MR) ratiois about 3% (refer to Non-patent Literature 1), and a low sensitivity asa magnetic sensor is a problem. However, recently, in an epitaxialCPP-GMR element of Heusler alloy layer/non-magnetic layer/Heusler alloylayer, obtained by growing a Co-based Heusler alloy (Co₂MnSi,Co₂(Fe_(0.4)Mn_(0.6))Si, Co₂Fe(Ga_(0.5)Ge_(0.5)), or the like) having ahigh spin polarizability on a MgO substrate as a ferromagnetic layer, amagnetoresistance ratio as large as 30 to 60% has been achieved (referto Non-patent Literatures 2 to 4). There is no other example of such amagnetoresistance element having a low resistance and a highmagnetoresistance ratio, and application thereof to various devices suchas a read head for a next-generation hard disc drive (HDD), having asurface recording density of 2 Tbit/inch² or more is expected highly.

However, an element utilizing a Heusler alloy electrode has such aserious problem that a high characteristic of a MR ratio of more than30% can be obtained only when a (001)-oriented monocrystalline thin filmmanufactured on an expensive (001)-MgO substrate is subjected to a heattreatment at 500° C. or higher. It is known that when a polycrystallineelement is manufactured on a generally used Si substrate with a thermaloxide film, a characteristic thereof is much poorer than that of amonocrystalline element (refer to Non-patent Literature 5). In addition,it has been reported that in a monocrystalline CPP-GMR element having aHeusler alloy as a ferromagnetic layer and having Ag as a spacer layer,a MR ratio largely depends on a crystal orientation and the highest MRoutput is obtained when a ferromagnetic layer is oriented in a (001)plane (refer to Non-patent Literature 6). A polycrystallinemagnetoresistance element oriented in a (001) plane has been alsoproposed due to such a background (Patent Literature 3). It is necessaryto manufacture a magnetoresistance element on a permalloy layer whichhas been electrodeposited as a magnetic shield for application to acurrently used read head for HDD. In this case, a ferromagnetic layer isa polycrystal oriented in (011). In addition, when a heat treatment isperformed at 350° C. or higher, diffusion of a permalloy layer,recrystallization, or the like occurs disadvantageously. Because ofthese, if a monocrystalline element having a ferromagnetic layeroriented in (001) can be grown on an inexpensive Si wafer, it isexpected that a magnetoresistance element having a large MR ratio can beachieved.

CITATION LIST Patent Literatures

-   -   Patent Literature 1: JP 5245179 B1    -   Patent Literature 2: WO 2012/093587 A1    -   Patent Literature 3: WO 2014/163121 A1

Non-Patent Literatures

-   -   Non-patent Literature 1: Yuasa et al., J. Appl. Phys. 92, 2646        (2002)    -   Non-patent Literature 2: Y. Sakuraba et al., Appl. Phys. Lett.        101, 252408 (2012)    -   Non-patent Literature 3: Li et al., Appl. Phys. Lett. 103,        042405 (2013)    -   Non-patent Literature 4: Du et al., Appl. Phys. Lett. 107,        112405 (2015)    -   Non-patent Literature 5: Du et al., Appl., Phys., Lett., 103,        202401 (2013)    -   Non-patent Literature 6: J. Chen et al., J. Appl., Phys., 115,        233905 (2014)

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The present invention solves the above problem, and an object thereof isto provide a monocrystalline magnetoresistance element having aferromagnetic layer required to achieve a high magnetoresistance ratiooriented in (001).

In addition, an object of the present invention is to provide amonocrystalline magnetoresistance element having a monocrystallineelement with (001) orientation similar to that on a MgO substrate on aSi substrate having a large diameter.

In addition, an object of the present invention is to provide a deviceusing the monocrystalline magnetoresistance element.

Means for Solving the Problems

For example, as illustrated in FIG. 1, a monocrystallinemagnetoresistance element according to an aspect of the presentinvention includes a silicon substrate 11, a base layer 12 having a B2structure, laminated on the silicon substrate 11, a first non-magneticlayer 13 laminated on the NiAl base layer 12 having a B2 structure, anda giant magnetoresistance effect layer 17 having at least one laminatelayer including a lower ferromagnetic layer 14, an upper ferromagneticlayer 16, and a second non-magnetic layer 15 disposed between the lowerferromagnetic layer 14 and the upper ferromagnetic layer 16.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, the silicon substrate 11 is preferably aSi(001) monocrystalline substrate. The base layer 12 having a B2structure preferably comprises at least one selected from the groupconsisting of NiAl, CoAl, and FeAl. The first non-magnetic layer 13preferably comprises at least one selected from the group consisting ofAg, V, Cr, W, Mo, Au, Pt, Pd, Ta, Ru, Re, Rh, NiO, CoO, TiN, and CuN.The lower ferromagnetic layer 14 preferably comprises at least oneselected from the group consisting of a Co-based Heusler alloy, Fe, andCoFe. The second non-magnetic layer 15 preferably comprises at least oneselected from the group consisting of Ag, Cr, Fe, W, Mo, Au, Pt, Pd, andRh. The upper ferromagnetic layer 16 preferably comprises at least oneselected from the group consisting of a Co-based Heusler alloy, Fe, andCoFe.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, preferably, the Co-based Heusler alloy isrepresented by formula Co₂YZ, and in the formula, Y comprises at leastone selected from the group consisting of Ti, V, Cr, Mn, and Fe, and Zcomprises at least one selected from the group consisting of Al, Si, Ga,Ge, and Sn.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, preferably, the base layer 12 having a B2structure has a film thickness of 10 nm or more and less than 200 nm,the first non-magnetic layer 13 has a film thickness of 0.5 nm or moreand less than 100 nm, the lower ferromagnetic layer 14 has a filmthickness of 1 nm or more and less than 10 nm, the second non-magneticlayer 15 has a film thickness of 1 nm or more and less than 20 nm, andthe upper ferromagnetic layer 16 has a film thickness of 1 nm or moreand less than 10 nm.

Here, a case where the base layer 12 having a B2 structure has a filmthickness of 200 nm or more makes surface roughness poorer, a case wherethe base layer 12 having a B2 structure has a film thickness of lessthan 10 nm is dominantly influenced by diffusion of the Si substrate andthe base layer 12 having a B2 structure, and a magnetoresistance ratiorequired for the present application cannot be obtained. A case wherethe first non-magnetic layer 13 has a film thickness of 100 nm or moremakes surface roughness poorer, a case where the first non-magneticlayer 13 has a film thickness of less than 0.5 nm does not form acontinuous film and cannot obtain an effect as a base layer, and amagnetoresistance ratio required for the present application cannot beobtained. A case where each of the lower ferromagnetic layer 14 and theupper ferromagnetic layer 16 has a film thickness of 10 nm or more islargely influenced by spin relaxation in the ferromagnetic layer, a casewhere each of the lower ferromagnetic layer 14 and the upperferromagnetic layer 16 has a film thickness of less than 1 nm has asmall effect of spin asymmetric scattering in the ferromagnetic layer,and a magnetoresistance ratio required for the present applicationcannot be obtained. A case where the second non-magnetic layer 15 has afilm thickness of 20 nm or more is largely influenced by spin relaxationin the non-magnetic layer, a case where the second non-magnetic layer 15has a film thickness of 1 nm or less generates a magnetic bond betweenthe upper ferromagnetic layer 16 and the lower ferromagnetic layer 14and reduces a magnetization relative angle, and a magnetoresistanceratio required for the present application cannot be obtained.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, preferably, the magnetoresistance ratio is 20%or more, and a resistance change-area product (ΔRA) is 5 mΩμm² or more.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, a diffusion preventing layer inserted betweenthe base layer having a B2 structure and the lower ferromagnetic layeris preferably further disposed.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, the diffusion preventing layer preferablycomprises at least one selected from the group consisting of Fe andCoFe.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, the diffusion preventing layer preferably hasa film thickness of 1 nm or more and less than 30 nm.

For example, as illustrated in FIG. 2, a method for producing amonocrystalline magnetoresistance element according to an aspect of thepresent invention includes a step of removing a natural oxide film ofthe silicon substrate 11 (S100), a step of setting the substratetemperature of the silicon substrate 11 to 300° C. or higher and 600° C.or lower (S102), a step of forming the base layer 12 having a B2structure on the silicon substrate 11 from which the natural oxide filmhas been removed at the substrate temperature (S104), a step of forminga film of a first non-ferromagnetic material on the silicon substrate onwhich the base layer 12 has been formed at the substrate temperature(S106), a step of forming a giant magnetoresistance effect layer havingat least one laminate layer including a lower ferromagnetic materiallayer, a second non-ferromagnetic material layer, and an upperferromagnetic material layer on the silicon substrate on which the filmof the first non-ferromagnetic material has been formed (S108), and astep of subjecting the silicon substrate on which the giantmagnetoresistance effect layer has been formed to a heat treatment at200° C. or higher and 600° C. or lower (S110).

Here, a case where the substrate temperature in the step of forming thebase layer 12 is lower than 300° C. does not cause single crystal growthof the base layer 12, a case where the substrate temperature in the stepof forming the base layer 12 is higher than 600° C. makes surfaceroughness of the base layer 12 poorer, and a magnetoresistance ratiorequired for the present application cannot be obtained. In addition, acase where the heat treatment temperature of the silicon substrate onwhich the giant magnetoresistance effect layer has been formed is lowerthan 200° C. does not cause atom regularization in the lowerferromagnetic layer or the upper ferromagnetic layer, a case where theheat treatment temperature of the silicon substrate on which themagnetoresistance effect layer has been formed is higher than 600° C.causes diffusion of the giant magnetoresistance effect layer, and amagnetoresistance ratio required for the present application cannot beobtained.

For example, as illustrated in FIG. 12, the method for producing amonocrystalline magnetoresistance element according to an aspect of thepresent invention preferably includes a step of forming a film of adiffusion preventing material on the silicon substrate 11 on which thebase layer 12 having a B2 structure has been formed at the substratetemperature (S106A) and a step of forming a film of a firstnon-ferromagnetic material on the silicon substrate 11 on which the filmof the diffusion preventing material has been formed at the substratetemperature (S106B) in place of the step of forming a film of a firstnon-ferromagnetic material on the silicon substrate 11 on which the baselayer 12 having a B2 structure has been formed at the substratetemperature (S106).

For example, as illustrated in FIG. 3, a monocrystallinemagnetoresistance element according to an aspect of the presentinvention includes a silicon substrate 21, a base layer 22 having a B2structure, laminated on the silicon substrate 21, and a tunnelmagnetoresistance effect layer 27 having at least one laminate layerincluding a lower ferromagnetic layer 24, an upper ferromagnetic layer26, and an insulating layer 25 disposed between the lower ferromagneticlayer 24 and the upper ferromagnetic layer 26, laminated on the baselayer 22 having a B2 structure.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, the silicon substrate 21 is preferably aSi(001) monocrystalline substrate. The lower ferromagnetic layer 24preferably comprises at least one selected from the group consisting ofa Co-based Heusler alloy, Fe, and CoFe. The insulating layer 25 is an ininsulator having a NaCl structure and a spinel structure, and preferablycomprises at least one selected from the group consisting of a MgO-basedoxide, Mg₂Al₂O₄, ZnAl₂O₄, MgCr₂O₄, MgMn₂O₄, CuCr₂O₄, NiCr₂O₄, GeMg₂O₄,SnMg₂O₄, TiMg₂O₄, SiMg₂O₄, CuAl₂O₄, Li_(0.5)Al_(2.5)O₄, γ-Al₂O₃, andmixtures thereof. The upper ferromagnetic layer 26 preferably comprisesat least one selected from the group consisting of a Co-based Heusleralloy, Fe, and CoFe.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, preferably, the Co-based Heusler alloy isrepresented by formula Co₂YZ, and in the formula, Y comprises at leastone selected from the group consisting of Ti, V, Cr, Mn, and Fe, and Zcomprises at least one selected from the group consisting of Al, Si, Ga,Ge, and Sn. In addition, preferably, the MgO-based oxide is representedby formula Mg_(1-x)Y_(x)O, Y comprises at least one selected from thegroup consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, and x is from0 to 0.3.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, preferably, the base layer 22 having a B2structure has a film thickness of 10 nm or more and less than 200 nm,the lower ferromagnetic layer 24 has a film thickness of 0.5 nm or moreand less than 50 nm, the insulating layer 25 has a film thickness of 0.5nm or more and less than 4 nm, and the upper ferromagnetic layer 26 hasa film thickness of 0.5 nm or more.

Here, a case where the base layer 22 having a B2 structure has a filmthickness of 200 nm or more makes surface roughness poorer, a case wherethe base layer 22 having a B2 structure has a film thickness of lessthan 10 nm is dominantly influenced by diffusion of the Si substrate andthe base layer, and a magnetoresistance ratio required for the presentapplication cannot be obtained. A case where the lower ferromagneticlayer 24 has a film thickness of 50 nm or more makes surface roughnesspoorer to thereby make it impossible to laminate the insulating layer 25flatly, a case where the lower ferromagnetic layer 24 has a filmthickness of less than 0.5 nm does not form a continuous film, and amagnetoresistance ratio required for the present application cannot beobtained. A case where the insulating layer 25 has a film thickness of 4nm or more makes a tunnel resistance too large, a case where theinsulating layer 25 has a film thickness of less than 0.5 nm makes aspin filter effect of the insulating layer 25 small, and amagnetoresistance ratio required for the present application cannot beobtained. In addition, a case where the upper ferromagnetic layer 26 hasa film thickness of less than 0.5 nm does not form a continuous film,and a magnetoresistance ratio required for the present applicationcannot be obtained.

In the monocrystalline magnetoresistance element according to an aspectof the present invention, the magnetoresistance ratio is preferably 50%or more.

For example, as illustrated in FIG. 4, a method for producing amonocrystalline magnetoresistance element according to an aspect of thepresent invention includes a step of removing a natural oxide film ofthe silicon substrate 21 (S200), a step of setting the substratetemperature of the silicon substrate 21 to 300° C. or higher and 600° C.or lower (S202), a step of forming the base layer 22 having a B2structure on the silicon substrate 21 from which the natural oxide filmhas been removed at the substrate temperature (S204), a step of forminga tunnel magnetoresistance effect layer having at least one laminatelayer including a lower ferromagnetic material layer, an insulatingmaterial layer, and an upper ferromagnetic material layer on the siliconsubstrate on which the base layer 22 has been formed (S206), and a stepof subjecting the silicon substrate on which the tunnelmagnetoresistance effect layer has been formed to a heat treatment at200° C. or higher and 600° C. or lower (S208).

A case where the substrate temperature in the step of forming the baselayer having a B2 structure is lower than 300° C. does not cause singlecrystal growth of the base layer, a case where the substrate temperaturein the step of forming the base layer having a B2 structure is higherthan 600° C. makes surface roughness of the base layer poorer, and amagnetoresistance ratio required for the present application cannot beobtained. In addition, a case where the heat treatment temperature ofthe silicon substrate on which the tunnel magnetoresistance effect layerhas been formed is lower than 200° C. has low crystallinity of theinsulating layer, a case where the heat treatment temperature of thesilicon substrate on which the tunnel magnetoresistance effect layer hasbeen formed is higher than 600° C. causes diffusion of the tunnelmagnetoresistance effect layer, and a magnetoresistance ratio requiredfor the present application cannot be obtained.

A device according to an aspect of the present invention uses the abovemonocrystalline magnetoresistance element.

The device is preferably any one of a read head used on a memoryelement, a magnetic field sensor, a spin electronic circuit, and atunnel magnetoresistance (TMR) device.

Effect of the Invention

A monocrystalline magnetoresistance element according to an aspect ofthe present invention can provide a monocrystalline magnetoresistanceelement having a monocrystalline element with (001) orientation, similarto that on a MgO substrate on a Si substrate having a large diameter,and can provide a fundamental monocrystalline magnetoresistance elementrequired for achieving mass productivity and low cost in order to applya monocrystalline giant magnetoresistance element using a Heusler alloyto an actual device.

In addition, the monocrystalline magnetoresistance element according toan aspect of the present invention forms a stable silicide on a Sisubstrate interface by using a layer having a B2 structure as a base,can produce a monocrystalline giant magnetoresistance element havingheat treatment resistance of 500° C. or higher and high interfaceflatness, and can obtain a characteristic equal to an element on a MgOsubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural cross section of a monocrystallinemagnetoresistance element having a giant magnetoresistance effect layeraccording to a first embodiment of the present invention;

FIG. 2 is a flowchart for explaining a method for producing themonocrystalline magnetoresistance element having a giantmagnetoresistance effect layer according to the first embodiment of thepresent invention;

FIG. 3 is a structural cross section of a monocrystallinemagnetoresistance element having a tunnel magnetoresistance effect layeraccording to a second embodiment of the present invention;

FIG. 4 is a flowchart for explaining a method for producing themonocrystalline magnetoresistance element having a tunnelmagnetoresistance effect layer according to the second embodiment of thepresent invention;

FIG. 5 illustrates an XRD pattern of a NiAl thin film grown on a Si(001)substrate at the substrate temperature of 300, 400, 500, or 600° C. inan Example of the present invention, and a RHEED image thereof;

FIG. 6 illustrates AFM images of a NiAl thin film grown on a Si(001)substrate at the substrate temperature of 300, 400, 500, and 600° C.,respectively in an Example of the present invention;

FIG. 7 illustrates RHEED images of an Ag layer grown on a Si(001)substrate/NiAl (50 nm) in an Example of the present invention, and AFMimages thereof after post-annealing;

FIG. 8 illustrates a cross section electron microscope image of aSi(001)/NiAl/Ag/CFGG/Ag/CFGG/Ag/Ru thin film in an Example of thepresent invention, and diffraction images of the layers using a nanobeam;

FIG. 9 illustrates a cross section electron microscope image of aCr/Ag/CFGG/Ag/CFGG/Ag/Ru monocrystalline thin film grown on a MgOsubstrate in a Comparative Example of the present invention, anddiffraction images of the CFGG layer;

FIG. 10 shows diagrams for explaining a magnetoresistance effect of aSi(001)/NiAl/Ag/CFGG/Ag/CFGG/Ag/Ru monocrystalline giantmagnetoresistance element (heat treatment temperature 400° C.) in anExample of the present invention;

FIG. 11 is a structural cross section of a monocrystallinemagnetoresistance element having a giant magnetoresistance effect layeraccording to a third embodiment of the present invention;

FIG. 12 is a flowchart for explaining a method for producing themonocrystalline magnetoresistance element having a giantmagnetoresistance effect layer according to the third embodiment of thepresent invention;

FIG. 13 is a diagram for explaining heat treatment temperaturedependency of a magnetoresistance effect of a giant magnetoresistanceelement in each of the third Example and Comparative Examples of thepresent invention;

FIG. 14 illustrates a transmission electron microscope image of a crosssection of a thin film in the third Example of the present invention,and energy dispersion spectrum element mapping images of constituentelements; and

FIG. 15 illustrates a transmission electron microscope image of a crosssection of a thin film in a Comparative Example of the presentinvention, and energy dispersion spectrum element mapping images ofconstituent elements.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, the present invention will be described with reference tothe drawings.

FIG. 1 is a structural cross section of a monocrystallinemagnetoresistance element having a giant magnetoresistance effect layeraccording to a first embodiment of the present invention. In FIG. 1, amonocrystalline magnetoresistance element 10 having a giantmagnetoresistance effect layer according to the present embodimentincludes a silicon substrate 11, a base layer 12 having a B2 structure,laminated on the silicon substrate 11, a first non-magnetic layer 13laminated on the base layer 12 having a B2 structure, a giantmagnetoresistance effect layer 17, and a cap layer 18. The giantmagnetoresistance effect layer 17 comprises a laminate layer including alower ferromagnetic layer 14, an upper ferromagnetic layer 16, and asecond non-magnetic layer 15 disposed between the lower ferromagneticlayer 14 and the upper ferromagnetic layer 16, but a plurality of thelaminate layers may be laminated. The giant magnetoresistance effectlayer 17 is located between the first non-magnetic layer 13 and the caplayer 18. Note that an upper electrode layer may be disposed on the caplayer 18, as necessary.

The silicon substrate 11 is a Si(001) monocrystalline substrate, and aSi substrate having a large diameter, such as a generally used Sisubstrate having a diameter of 8 inches can be used. The base layer 12having a B2 structure is a chemically stable material in which latticeconstants of NiAl, CoAl, and FeAl in the B2 structure are 0.288 nm,0.286 nm, and 0.295 nm, respectively, and lattice mismatch with aSi(001) plane is relatively satisfactorily less than 10%, and which hasa high melting point of higher than 1300° C. The base layer 12 having aB2 structure preferably has a film thickness of 10 nm or more and lessthan 200 nm. In the present invention, by employing the base layer 12having a B2 structure, a ferromagnetic layer having a body-centeredcubic lattice (bcc) structure as a basic structure can be formed on aSi(001) substrate as a monocrystalline thin film in a (001) direction ofa Miller index.

The first non-magnetic layer 13 preferably comprises at least oneselected from the group consisting of Ag, V, Cr, W, Mo, Au, Pt, Pd, Ta,Ru, Re, Rh, NiO, CoO, TiN, and CuN. The first non-magnetic layer 13preferably has a film thickness of 0.5 nm or more and less than 100 nm.

The lower ferromagnetic layer 14 preferably comprises of at least oneselected from the group consisting of a Co-based Heusler alloy, Fe, andCoFe. The lower ferromagnetic layer 14 preferably has a film thicknessof 1 nm or more and less than 10 nm.

The second non-magnetic layer 15 preferably comprises at least oneselected from the group consisting of Ag, Cr, W, Mo, Au, Pt, Pd, Ta, andRh. The second non-magnetic layer 15 preferably has a film thickness of1 nm or more and less than 20 nm.

The upper ferromagnetic layer 16 preferably comprises at least oneselected from the group consisting of a Co-based Heusler alloy, Fe, andCoFe. The upper ferromagnetic layer 16 preferably has a film thicknessof 1 nm or more and less than 10 nm.

The Co-based Heusler alloy is represented by formula Co₂YZ, and in theformula, preferably, Y comprises at least one selected from the groupconsisting of Ti, V, Cr, Mn, and Fe, and Z comprises at least oneselected from the group consisting of Al, Si, Ga, Ge, and Sn.

The cap layer 18 preferably comprises at least one selected from thegroup consisting of Ag, Cr, W, Mo, Au, Pt, Pd, Ta, and Rh. The cap layer18 preferably has a film thickness of 1 nm or more and less than 100 nm.When an upper electrode layer is disposed, Cu, Al, or the like oftenused as a material for an electrode is preferably used.

Next, a process for producing a device having such a structure will bedescribed.

FIG. 2 is a flowchart for explaining a method for producing themonocrystalline magnetoresistance element 10 having a giantmagnetoresistance effect layer according to the first embodiment of thepresent invention. In FIG. 2, first, in the first step, a natural oxidefilm of the silicon substrate 11 is removed (S100), and subsequently thesubstrate temperature of the silicon substrate 11 is maintained at 300°C. or higher and 600° C. or lower (S102). Then, a base layer having a B2structure is formed on the silicon substrate 11 from which the naturaloxide film has been removed at the above substrate temperature to formthe base layer 12 (S104). Subsequently, a film of a firstnon-ferromagnetic material is formed on the silicon substrate 11 onwhich the base layer 12 has been formed at the above substratetemperature (S106). The layer formed of the first non-ferromagneticmaterial corresponds to the first non-magnetic layer 13.

Subsequently, the giant magnetoresistance effect layer 17 having atleast one laminate layer including a lower ferromagnetic material layer,a second non-ferromagnetic material layer, and an upper ferromagneticmaterial layer is formed on the silicon substrate 11 on which the filmof the first non-ferromagnetic material has been formed (S108). Here,the layers formed of the lower ferromagnetic material, the secondnon-ferromagnetic material, and the upper ferromagnetic materialcorrespond to the lower ferromagnetic layer 14, the second non-magneticlayer 15, and the upper ferromagnetic layer 16, respectively.Subsequently, the cap layer 18 is formed on the silicon substrate onwhich the giant magnetoresistance effect layer 17 has been formed.Finally, the silicon substrate on which the giant magnetoresistanceeffect layer 17 and the cap layer 18 have been formed is subjected to aheat treatment as post-annealing at 200° C. or higher and 600° C. orlower (S110).

Next, a second embodiment of the present invention will be described.

FIG. 3 is a structural cross section of a monocrystallinemagnetoresistance element having a tunnel magnetoresistance effect layeraccording to the second embodiment of the present invention. Amonocrystalline magnetoresistance element 20 according to the secondembodiment includes a silicon substrate 21, a base layer 22 having a B2structure, laminated on the silicon substrate 21, a tunnelmagnetoresistance effect layer 27 laminated on the base layer 22 havinga B2 structure, and a cap layer 28. The tunnel magnetoresistance effectlayer 27 comprises a laminate layer including a lower ferromagneticlayer 24, an upper ferromagnetic layer 26, and an insulating layer 25disposed between the lower ferromagnetic layer 24 and the upperferromagnetic layer 26, but a plurality of the laminate layers may belaminated. The tunnel magnetoresistance effect layer 27 is locatedbetween the base layer 22 and the cap layer 28. Note that an upperelectrode layer may be disposed on the cap layer 28, as necessary.

Note that the silicon substrate 21, the base layer 22 having a B2structure, and the cap layer 28 in the second embodiment are similar tothe silicon substrate 11, the base layer 12 having a B2 structure, andthe cap layer 18 in the first embodiment, and therefore descriptionthereof will be omitted.

The tunnel magnetoresistance effect layer 27 includes the lowerferromagnetic layer 24, the insulating layer 25, and the upperferromagnetic layer 26. Note that the lower ferromagnetic layer 24 andthe upper ferromagnetic layer 26 in the tunnel magnetoresistance effectlayer 27 are similar to the lower ferromagnetic layer 14 and the upperferromagnetic layer 16 in the giant magnetoresistance effect layer 17,and therefore description thereof will be omitted.

The insulating layer 25 is an in insulator having a NaCl structure and aspinel structure, and preferably comprises at least one selected fromthe group consisting of a MgO-based oxide, Al₃O₄, Mg₂Al₂O₄, ZnAl₂O₄,MgCr₂O₄, MgMn₂O₄, CuCr₂O₄, NiCr₂O₄, GeMg₂O₄, SnMg₂O₄, TiMg₂O₄, SiMg₂O₄,CuAl₂O₄, Li_(0.5)Al_(2.5)O₄, γ-Al₂O₃, and mixtures thereof. Theinsulating layer 25 preferably has a film thickness of 0.5 nm or moreand less than 4 nm.

FIG. 4 is a flowchart for explaining a method for producing themonocrystalline magnetoresistance element 20 having a tunnelmagnetoresistance effect layer according to the second embodiment of thepresent invention. In FIG. 4, first, in the first step, a natural oxidefilm of the silicon substrate 21 is removed (S200), and subsequently thesubstrate temperature of the silicon substrate 21 is maintained at 300°C. or higher and 600° C. or lower (S202). Then, a base layer having a B2structure is formed on the silicon substrate 21 from which the naturaloxide film has been removed at the above substrate temperature to formthe base layer 22 (S204).

Subsequently, the tunnel magnetoresistance effect layer 27 having atleast one laminate layer including a lower ferromagnetic material layer,an insulating material layer, and an upper ferromagnetic material layeris formed on the silicon substrate on which the base layer having a B2structure has been formed (S206). Here, the layers formed of the lowerferromagnetic material, the insulating material, and the upperferromagnetic material correspond to the lower ferromagnetic layer 24,the insulating layer 25, and the upper ferromagnetic layer 26,respectively. Subsequently, the silicon substrate on which the tunnelmagnetoresistance effect layer 27 has been formed is subjected to a heattreatment as post-annealing at 200° C. or higher and 600° C. or lower(S208).

The present invention described in the first and second embodiments canbe used for a tunnel magnetoresistance element comprising a combinationof a ferromagnetic layer of (001)Fe, Co, or the like and amonocrystalline oxide barrier of MgO, MgAlO, or the like, and a currentperpendicular to plane-giant magnetoresistance element having a (001)Co-based Heusler alloy monocrystalline film as a ferromagnetic layer.Therefore, Examples will be described below.

EXAMPLES

In a first Example, a film of NiAl (thickness 50 nm) having a B2structure was formed on a Si(001) monocrystalline substrate from which anatural oxide film on a surface thereof had been removed with dilutedhydrofluoric acid at a substrate temperature of 300° C. to 600° C.

FIG. 5 illustrates an XRD pattern of the NiAl thin film grown on theSi(001) substrate at the substrate temperature of 300, 400, 500, or 600°C. in an Example of the present invention, and a RHEED image thereof.The vertical axis indicates an intensity (count), and the horizontalaxis indicates 2θ. As illustrated in FIG. 5, an X-ray diffractionpattern indicating single crystal growth of NiAl in a (001) directionand a streak of a reflection high energy electron diffraction (RHEED)image were observed at the substrate temperature of 400° C. to 600° C.On the other hand, an X-ray diffraction pattern indicating singlecrystal growth of NiAl in a (001) direction was not obtained but a peakin a (110) direction was obtained at the substrate temperature of 300°C.

FIG. 6 illustrates AFM images of a NiAl thin film grown on a Si(001)substrate at a predetermined substrate temperature in an Example of thepresent invention. (A) illustrates an image at the substrate temperatureof 300° C., (B) illustrates an image at the substrate temperature of400° C., (C) illustrates an image at the substrate temperature of 500°C., and (D) illustrates an image at the substrate temperature of 600° C.Surface roughness of the NiAl thin film was observed with an atomicforce microscope (AFM). As a result, average surface roughness (Ra) wasincreased as the heat treatment temperature was higher. That is, asillustrated in FIGS. 6(A) to (D), average surface roughness of 0.66 nmwas obtained at the substrate temperature of 300° C., average surfaceroughness of 1.17 nm was obtained at the substrate temperature of 400°C., average surface roughness of 2.19 nm was obtained at the substratetemperature of 500° C., and average surface roughness of 3.47 nm wasobtained at the substrate temperature of 600° C. Therefore, when singlecrystal growth of NiAl in a (001) direction was assumed, in themonocrystalline film, the smallest average surface roughness 1.17 nm wasobtained in the NiAl layer formed at 400° C. That is, in the NiAl thinfilm grown on the Si(001) substrate at the substrate temperature of 400°C. to 600° C., average surface roughness on a surface of the NiAl thinfilm was from 1 to 4 nm. Note that P-V indicates the largest filmthickness value in a Si(001) substrate measurement range of 5×5 μm² inFIGS. 6(A) to (D).

FIG. 7 illustrates RHEED images of an Ag layer grown on a Si(001)substrate/NiAl (50 nm) in an Example of the present invention, and AFMimages thereof after post-annealing. (A) is a cross section structuraldiagram for simply explaining a laminated state in the substrate. (B1)to (B3) are reflection high energy electron diffraction (RHEED) imagesof the layers. (C1) to (C5) are AFM images on a surface of the Ag layerwhich has been subjected to post-annealing at a predetermined heattreatment temperature. Here, the NiAl layer was formed at the substratetemperature of 500° C. The Ag layer was formed at room temperature, andthen was subjected to post-annealing at 300° C. to 600° C. FIG. 7 (B1)illustrates a RHEED image of the Ag layer in a [100] direction of aMiller index, FIG. 7 (B2) illustrates a RHEED image of the NiAl layer ina [110] direction of a Miller index, and FIG. 7 (B3) illustrates a RHEEDimage of the Si substrate in a [110] direction of a Miller index.(001)-oriented single crystal growth of Ag on NiAl was confirmed.

In addition, in the AFM images in FIG. 7, (C1) illustrates averagesurface roughness just after a film was formed. The average surfaceroughness was 0.94 nm in a case where a measurement range was 1×1 μm²,and the average surface roughness was 1.15 nm in a case where ameasurement range was 5×5 μm². In (C2), the average surface roughnesswas 0.41 nm after post-annealing at 300° C. In (C3), the average surfaceroughness was 0.33 nm after post-annealing at 400° C. In (C4), theaverage surface roughness was 0.29 nm after post-annealing at 500° C. In(C5), the average surface roughness was 0.39 nm after post-annealing at600° C. Surface flatness was largely improved due to the Ag layer, andthe average surface roughness Ra was improved to 0.29 nm bypost-annealing at 500° C. Therefore, a range of the post-annealingtemperature is preferably from 300° C. to 600° C.

FIG. 8 illustrates cross section electron microscope images of a Sisubstrate/NiAl/Ag/Co₂FeGa_(0.5)Ge_(0.5)(CFGG)/Ag/CFGG/Ag/Ru giantmagnetoresistance element film as an example of the magnetoresistanceelement, and diffraction images of the layers. In FIG. 8, (A)illustrates a cross section electron microscope image, (B1) illustratesa diffraction image of the Ag layer in a [100] direction of a Millerindex, (B2) illustrates a diffraction image of the CFGG layer in a [110]direction of a Miller index, (B3) illustrates a diffraction image of theAg layer in a [100] direction of a Miller index, (B4) illustrates adiffraction image of the CFGG layer in a [110] direction of a Millerindex, (B5) illustrates a diffraction image of the Ag layer in a [100]direction of a Miller index, (B6) illustrates a diffraction image of theNiAl layer in a [110] direction of a Miller index, (B7) illustrates adiffraction image of an interface between the Si substrate and the NiAllayer, (B8) illustrates a diffraction image of NiSi₂ (CaF₂, space group:Fm-3m) in a [110] direction of a Miller index, and (B9) illustrates adiffraction image of the Si substrate in a [110] direction of a Millerindex.

FIG. 9 illustrates a cross section electron microscope image of aCr/Ag/CFGG/Ag/CFGG/Ag/Ru monocrystalline thin film grown on a MgOsubstrate in a Comparative Example of the present invention, anddiffraction images of the CFGG layer. (A) illustrates a cross sectionelectron microscope image. (B) illustrates a diffraction image of anupper CFGG layer. (C) illustrates a diffraction image of a lower CFGGlayer. Comparison between FIG. 8(A) and FIG. 9(A) indicates thatlaminated films having almost equal interface flatness were produced inFIG. 8(A) and FIG. 9(A). In addition, it is confirmed that all thelayers were (001)-oriented films obtained by single crystal growth fromdiffraction images of the layers. As illustrated in FIG. 8 (B7), it wasfound that Ni was diffused to a Si substrate side to form NiSi₂ in aninterface layer of the Si substrate/NiAl layer. This NiSi₂ layer wasformed when the NiAl layer was formed on the Si substrate at thesubstrate temperature of 500° C. Therefore, it is considered that theNiSi₂ layer is stable even at a heat treatment temperature of 500° C. toCFGG/Ag/CFGG and serves as a diffusion preventing layer of the NiAl andthe Si substrate.

FIG. 10 illustrates a result of MR measurement of a monocrystallineCFGG/Ag/CFGG CPP-GMR element grown on a Si substrate. In (A), thevertical axis indicates a magnetoresistance MR ratio, and the horizontalaxis indicates a heat treatment temperature of the Si substrate. In (B),the vertical axis indicates a resistance (Ω), and the horizontal axisindicates a magnetic field (Oe). At a heat treatment temperature of 400°C. to CFGG/Ag/CFGG, the MR ratio was 28%, the resistance change-areaproduct (ΔRA) was 8.7 mΩμm². Characteristics almost equal to those ofthe monocrystalline element produced on a MgO substrate could beobtained.

Next, a third embodiment of the present invention will be described.FIG. 11 is a structural cross section of a monocrystallinemagnetoresistance element having a giant magnetoresistance effect layeraccording to the third embodiment of the present invention. In FIG. 11,note that the same sign will be given to a component having the samefunction as in FIG. 1, and description thereof will be omitted.

In FIG. 11, a CoFe layer as a diffusion preventing layer 12A isinterposed between a base layer 12 having a B2 structure and a firstnon-magnetic layer 13. The CoFe layer preferably has a film thickness of1 nm or more and less than 30 nm. A case where the CoFe layer has a filmthickness of less than 1 nm does not form a continuous film, and adiffusion preventing effect required for the present application cannotbe obtained. A case where the CoFe layer has a film thickness of 30 nmor more makes surface roughness poorer, and thereby makes it difficultto laminate a giant magnetoresistance effect layer 17 flatly.

FIG. 12 is a flowchart for explaining a method for producing themonocrystalline magnetoresistance element having a giantmagnetoresistance effect layer according to the third embodiment of thepresent invention. In FIG. 12, note that the same sign will be given toa component having the same function as in FIG. 2, and descriptionthereof will be omitted.

As illustrated in FIG. 12, the method for producing the monocrystallinemagnetoresistance element according to the third embodiment preferablyincludes a step of forming a film of a diffusion preventing material ona silicon substrate 11 on which a base layer 12 having a B2 structurehas been formed at the substrate temperature (S106A) and a step offorming a film of a first non-ferromagnetic material on the siliconsubstrate 11 on which the film of the diffusion preventing material hasbeen formed at the substrate temperature (S106B) in place of the step offorming a film of the first non-ferromagnetic material on the siliconsubstrate 11 on which the base layer 12 having a B2 structure has beenformed at the substrate temperature, illustrated in FIG. 2 (S106). Byforming the film of the diffusion preventing material, a film structurein which the diffusion preventing layer 12A is interposed between thebase layer 12 having a B2 structure and the first non-magnetic layer 13is obtained.

FIG. 13 is a diagram for explaining heat treatment temperaturedependency of a magnetoresistance effect of a giant magnetoresistanceelement in each of the third Example and Comparative Examples of thepresent invention. The horizontal axis indicates an annealing treatmenttemperature, and the vertical axis indicates a resistance change-areaproduct (ΔRA).

The third Example of the present invention is an epi-type giantmagnetoresistance element film which is a single crystal obtained bylaminating Si(001)/NiAl/CoFe/Ag/CFGG/Ag/CFGG/Ag/Ru, and is indicated byan open star mark, ⋆, in FIG. 13. Comparative Example 1 is an epi-typegiant magnetoresistance element film which is a single crystal obtainedby laminating Si(001)/NiAl/Ag/CFGG/Ag/CFGG/Ag/Ru, and is indicated by afilled star mark, ★, in FIG. 13. Comparative Example 2 is an epi-typegiant magnetoresistance element film which is a single crystal obtainedby laminating MgO(001)/NiAl/Ag/CFGG/Ag/CFGG/Ag/Ru, and is indicated by afilled square mark, ▪, in FIG. 13. Comparative Example 3 is apolycrystalline giant magnetoresistance element film which has beensubjected to an insitu annealing treatment, and is indicated by a filledtriangle mark, ▴, in FIG. 13. Comparative Example 4 is a polycrystallinegiant magnetoresistance element film which has been subjected to anexsitu annealing treatment, and is indicated by a filled circle mark, ●,in FIG. 13. Comparative Example 5 is a polycrystalline giantmagnetoresistance element film when crystal growth occurs in a(011)-oriented film, and is indicated by a filled rhomboid mark, ♦, inFIG. 13.

In the third Example of the present invention, by disposing the CoFelayer as the diffusion preventing layer 12A between the base layer 12having a B2 structure and the first non-magnetic layer 13, even when theannealing treatment temperature is within a range of 450° C. to 550° C.higher than 400° C., the resistance change-area product (ΔRA) ismaintained at a characteristic equal to or slightly better than a casewhere the annealing treatment temperature is 400° C. Meanwhile, inComparative Example 1, the laminate structure is equal to that in thethird Example of the present invention except that the diffusionpreventing layer 12A is not included, but when the annealing treatmenttemperature is within a range of 450° C. to 550° C. higher than 400° C.,the resistance change-area product (ΔRA) is poorer than a case where theannealing treatment temperature is 400° C. In Comparative Example 2,expensive MgO(001) is used in place of silicon(001) as a substrate, butannealing treatment temperature dependency of the resistance change-areaproduct (ΔRA) is equal to that in the third Example of the presentinvention.

In Comparative Examples 3 to 5, polycrystalline giant magnetoresistanceelement films are used, and therefore the resistance change-area product(ΔRA) is much lower than that in the third Example of the presentinvention.

FIG. 14 illustrates cross sections of a thin film according to the thirdExample of the present invention. (A) illustrates a transmissionelectron microscope image. (B) illustrates energy dispersion spectrumelement mapping images of constituent elements. As the constituentelements, Ru, Ag, and Co are indicated from the left side of the upperrow toward the right side of the upper row, Fe, Ga, and Ge are indicatedfrom the left side of the middle row toward the right side of the middlerow, and Ni, Al, and Si are indicated from the left side of the lowerrow toward the right side of the lower row.

Presence of the CoFe layer as the diffusion preventing layer 12Aprevents diffusion of Al from the NiAl layer as the base layer 12 havinga B2 structure to the Ag layer as the first non-magnetic layer 13.

FIG. 15 illustrates cross sections of a thin film in a ComparativeExample of the present invention. (A) illustrates a transmissionelectron microscope image. (B) illustrates energy dispersion spectrumelement mapping images of constituent elements. Note that an arrangementrelation among the constituent elements in FIG. 15(B) is similar to thatin FIG. 14(B).

Because of no presence of the CoFe layer as the diffusion preventinglayer 12A, when the annealing treatment temperature is as high as 400°C., diffusion of Al occurs from the NiAl layer as the base layer 12having a B2 structure to the Ag layer as the first non-magnetic layer13.

The (001)-oriented monocrystalline magnetoresistance element on the Sisubstrate, produced in the present invention is formed of NiAl baselayer/Ag base layer/magnetoresistance element film/cap layer, but has apossibility that the layers can be replaced as follows.

The Ag base layer can be replaced with a material which can cause(001)-oriented single crystal growth on NiAl. For example, in a singlematerial having lattice mismatch of less than 10% with NiAl, such as abcc material including Cr, Fe, W, and Mo, or a fcc material includingAu, Pt, Pd, and Rh, single crystal growth is expected. Therefore, the Agbase layer can be replaced with such a single material or a laminatedstructure thereof.

The magnetoresistance element can be applied to all the combinations ofa ferromagnetic body and a non-magnetic body or an insulator, having alattice constant similar to the base layer. As the ferromagnetic body, aHeusler alloy other than CFGG, such as Co₂MnSi or Co₂FeAl, and a generalferromagnetic body having a bcc structure, such as Fe or CoFe can beused. Application is possible to all the other spacers having excellentlattice match, such as NiAl, AgZn, CuZn, or Ag₃Mg as a non-magneticintermediate layer in addition to Ag. In addition, also when MgO orMg₂AlO_(x) is used as a tunnel barrier layer of a tunnelmagnetoresistance element, lattice match is obtained. Therefore, amonocrystalline tunnel magnetoresistance element can be grown on a Sisubstrate.

INDUSTRIAL APPLICABILITY

The monocrystalline magnetoresistance element according to an aspect ofthe present invention is obtained by epitaxially growing a (001) planeof a body-centered cubic lattice ferromagnetic layer on a Simonocrystalline substrate having a large diameter, is inexpensive, andis suitable for mass-supply. Therefore, the monocrystallinemagnetoresistance element is preferably used for a practical device suchas a magnetic head using a tunnel magnetoresistance element or a currentperpendicular to plane-giant magnetoresistance element, a magnetic fieldsensor, a spin electronic circuit, or a tunnel magnetoresistance device.

1-8. (canceled)
 9. A magnetoresistance element comprising: a siliconsubstrate; a base layer having a B2 structure, laminated on the siliconsubstrate; and a tunnel magnetoresistance effect layer having at leastone laminate layer including a lower ferromagnetic layer, an upperferromagnetic layer, and an insulating layer disposed between the lowerferromagnetic layer and the upper ferromagnetic layer, laminated on thebase layer having a B2 structure.
 10. The magnetoresistance elementaccording to claim 9, wherein the silicon substrate is a Si(001)monocrystalline substrate, the lower ferromagnetic layer comprises atleast one selected from the group consisting of a Co-based Heusleralloy, Fe, and CoFe, the insulating layer is an insulator having a NaClstructure and a spinel structure, and comprises at least one selectedfrom the group consisting of a MgO-based oxide, Al₃O₄, Mg₂Al₂O₄,ZnAl₂O₄, MgCr₂O₄, MgMn₂O₄, CuCr₂O₄, NiCr₂O₄, GeMg₂O₄, SnMg₂O₄, TiMg₂O₄,SiMg₂O₄, CuAl₂O₄, Li_(0.5)Al_(2.5)O₄, and γ-Al₂O₃, and the upperferromagnetic layer comprises at least one selected from the groupconsisting of a Co-based Heusler alloy, Fe, and CoFe.
 11. Themagnetoresistance element according to claim 8, wherein the Co-basedHeusler alloy is represented by formula Co₂YZ, and in the formula, Ycomprises at least one selected from the group consisting of Ti, V, Cr,Mn, and Fe, and Z comprises at least one selected from the groupconsisting of Al, Si, Ga, Ge, and Sn. The magnetoresistance elementaccording to claim 10, wherein the MgO-based oxide is represented byformula Mg_(1-x)Y_(x)O, Y comprises at least one selected from the groupconsisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, and x is from 0 to0.3.
 12. The magnetoresistance element according to claim 11, whereinthe base layer having a B2 structure has a film thickness of 10 nm ormore and less than 200 nm, the lower ferromagnetic layer has a filmthickness of 0.5 nm or more and less than 50 nm, the insulating layerhas a film thickness of 0.5 nm or more and less than 4 nm, and the upperferromagnetic layer has a film thickness of 0.5 nm or more.
 13. Themagnetoresistance element according to claim 9, having amagnetoresistance ratio of 50% or more.
 14. (canceled)
 15. A deviceusing the magnetoresistance element according to claim
 9. 16. (canceled)17. The device according to claim 15, wherein the device is any one of aread head used on a memory element, a magnetic field sensor, a spinelectronic circuit, and a tunnel magnetoresistance (TMR) device.